


Crashed

by itbeajen



Series: Osamutober [2020] [7]
Category: Haikyuu!!
Genre: F/M, Fluff, Osamutober, Reader-Insert, mermaid au, merman au
Language: English
Status: Completed
Published: 2020-10-07
Updated: 2020-10-25
Packaged: 2021-03-07 19:13:30
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 12,961
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26852740
Author URL: https://archiveofourown.org/users/itbeajen/pseuds/itbeajen
Summary: He had no idea that he’d be the one getting attracted to a human.
Relationships: Miya Osamu/Reader
Series: Osamutober [2020] [7]
Series URL: https://archiveofourown.org/series/1948825
Comments: 19
Kudos: 110
Collections: Osamutober





	1. Chapter 1

**Author's Note:**

> Prompt #7 for Osamutober
> 
> Mermaid/Merman AU

His thoughts shuddered to a stop as he realized the sloping sands were gradually increasing in height, a clear indication that was getting increasingly closer to shore. With just one more powerful stroke from his tail, he could potentially be on the shores. Perhaps he could even feel the sun on his back, like he has heard from the tales that their people have brought back. But he was still.. Scared. Something deep within him discouraged him from crossing that last span of distance between him and the shore. Something pushed him away from the land, as though it was too dangerous for even him to handle. 

He languidly swam parallel to the sand, all the while simultaneously ravaging the sandy dunes for crabs and smaller mussels that have slowly been drifting upwards, soon to be washed ashore. Mid-harvesting, he finds himself distracted by a muffled melody. His head slowly turned around and he slowly turned his body in the direction of the source of the sound. It was a song of some sort, and it was enrapturing, as though he was being lured in by a softer yet muffled sound. He stops foraging and glances up past the veil of water that hid him from sight. Wherever the sound was coming from, it was appealing, almost enchanting… but it came from above - it came from land. 

He finished off what food he had in his hands before slowly following the sound closer and closer to shore.  _ I… recognize this tune. _ He hummed along with it, although choppily as he forgot bits and pieces of it. It wasn’t helpful that the water muffled him either. He hummed a few times more before slowly making his way towards the small isolated alcove on the beach. He can hear it almost clearly now, and though the language was not one he recognized, he did know that the tune was almost identical to the one he grew up with, if not for the slight change in tempo and octave.

His curiosity got the best of him as his head slowly broke the water’s surface. At first, he was content with just being able to hear the sound properly, but as soon as he finally peeked out over the surface of the waves, his eyes widened in surprise to see that the source of such a beautiful song was coming from a human being. 

There you were, a human sitting on an outcrop of rocks, and appeared to be teetering dangerously on the edge of it, almost close enough to jump into the water. Yet there was no fear, no anxiousness exuding from her being as she appeared to be content atop the rocks. Osamu couldn’t help but watch in wonder as your hand continued to move over a strange black slab that appeared to have smaller white slabs within it. All the while, your lips moved and created the beautiful sound that had captivated him, yet felt as familiar to him as the water enveloping him did - as though it was something he had grown up with and was a part of his life for as long as he knew it. 

Whether or not he knew that he was slowly drifting towards the shore, no one would be able to tell him. But the sudden feeling of the cool breeze against the tip of his tail fin shocks him out of his stupor and out of instinct, he immediately dives below the waves, churning them with bubbles in his wake. He feels his heart beat racing at the mere thought of potentially getting caught, but there is a tug at his heart strings when he catches a glimpse of the expression on your face.

Your eyes were filled with shock as your gaze was finally ripped away from your original object of focus. Your hair that was formerly held back with one hand was suddenly set loose and fluttered in the wind as you tried to catch a sight of what was out there. But what he felt most strongly about was not regret for startling and surprising you, rather it was regret mixed with guilt for being the reason as to why you had stopped your song. A small sigh leaves Osamu as he quickly makes his way back to deeper waters. He won’t tell them about this encounter, they’d definitely be worried. Yet his thoughts kept returning to the sound of your voice and the familiarity of it. Despite the threats and dangers that the shore may bring, he couldn’t help but hope that perhaps there will be a next time in which he finds the human with the beautiful voice.

Meanwhile, you couldn’t help but stare at the area where you swore you saw silver - a shimmer, nearly translucent silver that reminded you of the waning moonlight in the sky. Yet you could do nothing more than curiously stare down at the lapping waves on shore before retreating further inland. Perhaps it was nothing more than your imagination, but you desperately hoped that it was real, and not just a figment of your imagination.

***

“What did I tell you about going too close to shore?” Kita sighed. 

“I know, it’s just…” Osamu struggled to explain himself. He knew for a fact that he’d get yelled at regardless and he softly mumbled, “That human was singing our song.”

Kita’s eyes widened and he shook his head, “That shouldn’t be possible.”

He flicked his tail in contemplation, unintentionally creating a small tornado of water and he sighed, “Well, as much as I’d like to rule it out as being impossible, do some investigating for me, won’t you, Osamu?”

“Sure,” Osamu was surprised by the command, and he had to refrain himself from making any movement that was indicative of his excitement. He didn’t know how to explain it, but it was… fascinating and exciting to be able to potentially meet a human. Of course, he couldn’t bring you down here with him, but he’s sure he can try to communicate with you.

As Kita swam off to check on the other members who had also returned from foraging, his twin swam up to him and asked, “So you found a human?”

“I did, she was singing the same song that Kita’s grandmother used to sing to us when we were babies.”

Atsumu’s eyes widened and after contemplating the idea for a few seconds he shook his head and waved his hand in dismissal. “No, no, there’s no way, that’s the song of  _ our  _ people, there’s no way some dumb human would know it.”

“Yet that ‘dumb’ human was singing it word for word,” Osamu pointed out. Atsumu rolled his eyes and mumbled, “Whatever, I’ll go with ya to make sure nothing bad happens.”

***

“Are you heading down to that beach again?”

“Yeah!”

You had called out to your mother and she sighed, “You… you’re so obsessed with that beach, just like your grandmother was.”

You glanced back and you could see her fondly shaking her head and she teased, “Is staying inside that boring for you?”

“The TV is so loud I can’t focus on reading, mom! Besides, it’s just down below, you can see me from the cliffside if you get worried about me,” you smiled as you readjusted your small bag. There was a sandwich you packed for lunch and some portable chargers for your phone just in case and your mom walked up to give you a kiss on your forehead. As she took a step back, and her smile dropped slightly, “Don’t get your books wet.”

“I won’t!” you responded with a determined tone. You could see the concern in your mother’s eyes and you softly reassured her, “I won’t go in, I promise.”

She nods and sighs before fondly shaking her head. The smile is back on her face, and you mirror the expression as you left the house with a slight spring in your step. Ever since that day at the beach where you swear you saw a flicker of silver scales, you’ve been returning to that same alcove relatively often. While you know it could have just been a flicker of light on the sea shore, at the same time you can’t help but feel like it was something else. 

You avoid the same outcrops of rocks that you had sat at last time. After all, it wasn’t worth getting sprayed by the waves that crashed onto the rocks that kept interrupting your drawing time. As you climbed over the rocks, you found a small patch of sand that was hidden away from the general view of the beach, but still visible from where your house was located. 

“This looks like a good place to start sketching,” you mumbled as you took out a towel and began to lay it out on the sand. You plopped onto the towel and immediately pulled out a few pencils and your sketchbook. You didn’t have anything in mind for sketching, but you knew that you did want to imagine what it was that you saw.  _ A mermaid? A sea serpent?  _

You hummed lightly, it was the same tune you always found yourself humming whenever you were here. Perhaps it was because the tune fit so well with the atmosphere the beach gave you, but whatever it was, that was just how you felt and nothing could really change that.

As you get deeper into your drawing, you don’t notice the ripples far out from the shore. The Miya twins have their heads poked out above water and Atsumu’s eyes widened upon hearing the soft humming coming from you and he muttered, “Well shit, you were right.”

“Told ya.”

“What are we going to do?”

“Well… we can’t approach her, she’s gonna freak out.”

“Well I mean, we can’t just  _ stay here _ and watch her for hours. We still got to go gather food.”

“Kita told us to gather information, but he didn’t exactly say how,” Osamu muttered and Atsumu groaned, “Do you have the ability to conjure legs?”

“I don’t have human clothes! Do I look like I’d just magically have clothes on me?”

“This was your mission, why didn’t ya come prepared, you fool?!”

“I’m the fool?” Osamu growled and lunged at his twin, “You’re the one who stupidly followed me! Just go and do your own stuff and-”

Osamu stops mid-sentence when Atsumu flicks his tail in his direction, summoning a wave of water to slam onto his face. He shakes his head, ignoring the sensation, but then stops upon seeing the shock on Atsumu’s face. Osamu narrows his eyes in irritation and grumbled, “What are you so shocked about?”

Atsumu merely points towards the beach before diving below water without a single explanation or apology to his twin. Osamu glances away from Atsumu and then to the beach and sees you blinking in his direction. Your gaze refused to break away, but your voice certainly did. You stopped humming your song and you softly asked, “Are you… the same person I saw the other day?”

Osamu’s eyes widened and he glanced down to where Atsumu was hiding beneath the water and he wildly waved his hands before swimming off. Osamu deadpanned, of course his twin would be absolutely useless when he actually needs him. Osamu nervously turns back to you and you softly mumble, “Sorry if I startled you, I just… didn’t think you guys were real.”

“You’re not scared?” Osamu asked. You shook your head and you glanced around. There was no one else around and you let out a sigh of relief and you responded, “No, but you shouldn’t stay around. Shouldn’t you be further away from shore? This is dangerous for you isn’t it?”

Osamu’s eyes widened and he asked, “How much do you know about us?”

Osamu swears he saw a flicker of emotion, but you give him a weak smile and shake your head, “Not much, just… childhood stories.”

_ Childhood stories? _

Osamu wanted to ask more, but he could tell you were nervous, perhaps not for yourself, but more so for him. He sighed and asked, “What’s your name?”

“I’m [Name], what about you?”

“Osamu,” Osamu responded and you softly whispered his name into the ocean breeze as it carried it away. He couldn’t hear it, he wasn’t close enough to, but after seeing your soft wistful smile on his face, he knew that he couldn’t go any closer. 

“You should go back, Osamu,” you glanced at the sky and your gaze returned to him and your mouth opened for a moment before you quickly closed it. You bit your lower lip. As much as you wanted to ask him if you could meet up with him, you knew that you couldn’t. Your curiosity was so strong, yet you knew better than to ask. 

Osamu nodded and he dove back underwater. He wanted to ask. He wanted to know more. But for now… he supposes the best choice of action was to leave. As he dove back beneath the surface, he glared at his twin who was a few feet away.

“Did she notice us?!”

“Of course she did, no thanks to you. Kita always tells us to be more careful with our swings yet you never listen!”

“Look at least, at least she doesn’t look like a bad person?”

“You’re one to talk when ya straight up  _ abandoned _ me.”

“Alright, alright, sorry Samu, but are you really going to try to talk to her again?”

“She seemed to have knowledge of us… I need to report back to Kita about her.”

***

“Osamu, over here,” you waved him down after seeing the shimmer of silver break the surface. The two of you have begun to meet up in the more secluded part of the beach, aka the outcropping of rocks where he had found you the first time. In the few days you’ve known each other, Osamu has learned nothing that would gleam into why you knew so much about his kind. 

Yet he learned so much about you that he finds himself oddly at peace with you, even if he didn’t find out the truth sooner, he wouldn’t mind these excursions. Osamu knew of how much you loved the sea, yet you wouldn’t ever go in it - or at least, not around him. He knew of how your family was only ever here during the summers, to visit your grandmother since it was her house that you stayed at. 

He found you extremely intriguing, and honestly he can’t help himself when he gets more invested in visiting you every day.

He slowly made his way up to the rock and found the same shallow tides to sit upon. You inched as close as you could to the water side and Osamu asked, “Why not just sit in the shallow area with me? Don’t you humans have swimsuits or whatever it is you told me about?”

“I don’t want to ruin this sundress my mother got me, and I mean… we do, but…” your voice trailed off and Osamu can see that you’re biting your lower lip again and he muttered, “You don’t hafta talk about it you don’t want to. ‘Sides, if you keep biting your lip like that, you’re going to start bleeding.”

“O-Oh,” you stopped and you sheepishly smiled, “Sorry, I just… well, I was always told to stay away from water, but… I can’t help but come back. And well, I know why I was always told not to”

You slowly dip your hand into the water and scoop it up, and at that moment, Osamu could see why. Maybe you couldn’t see properly, but he saw for a split second the same scales that covered the back of his palm were faintly visible on your hand too. 

You leave your hand in the water and you ask, “You see it right?”

“You’re… You’re a mermaid.”

“Yes, and no. I’m… I’m a fourth. My grandfather was a merman who fell in love with my grandmother when she was on this same beach. But grandfather couldn’t stay with us forever, so he had eventually returned to sea. He still comes back to visit, so it’s not like we never get to see him. Plus, Grandmother never hated him for it, she had told us she knew what kind of situation she was getting into.”

“So your mother is half.”

“Mhm,” you nodded and you heaved a sigh, “But mom doesn’t have any of grandfather’s genes. We just assumed that a mermaid’s genes weren’t dominant enough to show up. And then… and then I was born.”

You glanced at the ocean and Osamu could see it again, the same wistfulness that he had noticed over the time he spent with you. He carefully took your hand in his to inspect and he doesn’t miss how you startled a bit. Close up, he could see it better, the scales had a crystal opal-like sheen to it and he asked, “Have you not gone into the water since then?”

You shook your head and you softly mumbled, “I don’t know how to use my tail, and grandmother and mother didn’t know what to do, so I just stopped going to the beach. It’s only seawater that activates my transformation, and honestly it’s terrifying.”

You finally look away from your hand and turn your gaze to him. He meets your gaze and is surprised by the tears at the corner of your eyes. 

“Are you cr-”

“No! I’m just… emotional. I don’t ever talk about this to my family, so being able to talk to you about it… it just makes me really happy that I have someone I can confide my worries to about this. I can’t just tell people I turn into a mermaid when I touch the water you know.”

Osamu’s eyes widened and he turned your hand over in his and he was determined. Even if you were scared, even if you were unsure, he was going to teach you to swim. You were one of them, there was no reason for you to be so fearful of the ocean that is also your home. 

“Don’t hate me for this, [Name].”

“Huh?” 

Your heart felt constricted. Did you confide too much? Maybe he was offended that you were only a fraction of a mermaid and not a real one. You opened your mouth to apologize, but before you could, you feel him pull on your hand and you fall into the water with a startled yelp. You frantically kick to the surface, but you feel the same excruciating pain that you felt the very first time.

_ It hurts. It hurts. It hurts.  _ Your thoughts are scrambled and all you can think about is the pain in your lower body as the scales that haven’t surfaced for years were suddenly deciding to transform you now that you were suddenly thrown into the water.  _ Is this punishment for telling him I was only a fraction?!  _

"[Name]!" Osamu didn't expect the transformation to be so painful for you. The few times he had attempted to switch to human legs, it just felt like his tail slipped off.  _ She- She can't breathe?! _

Osamu pulled you up to the air, but you were struggling against him as you were still focused only on the pain. Your legs felt like they were being stabbed by thousands of needles all while being on fire. 

_ Fuck, she won't surface because she's in pain.  _ Osamu quickly surfaced and took in a deep breath and dove back beneath the surface.  _ Forgive me, [Name], but it's either this or you might drown. _

He cups your cheeks, and forces his mouth over yours. It was almost like CPR, but the shock of the action startled you completely out of the pain and your eyes widened in surprise. 

By the time he parts, you end up gasping in shock, only to realize that you could breathe. Your eyes widened and he softly asked, "Are you okay?"

You struggled to process what was going on. But that crystal opalescent tail below you, is that yours? You reached out to touch your tail only to be even more surprised when you see the same sheen on the scales that covered parts of your forearm and hands.

"Is this me? Wait," you glanced over to him and asked, "I can breathe?"

"I.. I guess you can?" Osamu weakly responded and he felt his face burning.  _ Did I kiss her for no reason?? _ He dragged a hand down his face and groaned, "Fuck me. I am so sorry for that kiss, [Name]."

"It's- it's okay! You did it for a good reason, I-" your thoughts cut off as you noticed you were slowly sinking. The light from above got dimmer and dimmer, but the way the sunlight filtered through was amazing. 

"Uh, [Name]?" Osamu gently grabbed your hands, "You're sinking right now."

"How do I… How do I use my tail?" You awkwardly asked. Osamu looked at your tail and then you. Upon meeting your gaze, he burst into laughter and said, "We can work on that."

He gently wraps an arm around you and pulls you flush up to him, and you’re more than thankful right now that you were still wearing your sundress. You could feel his warmth from his body that contrasted strongly with the coldness of the sea water around you. As one arm reached around you, his eyes widened and he softly mumbled, “I think your dress is ruined.”

“Eh? Why?”

“You,” Osamu was glancing at your back and he whispered, “You have a dorsal fin, just like me.”

“What?!”

You scrambled to reach behind your back and was surprised when your fingertips grazed the tip of the dorsal. Your eyes widened and Osamu doesn’t miss the slight gasp before he gently reminds you, “Hold on tight, I’ll bring us back up to the surface.”

“O-oh, okay,” you tentatively placed your hand on his shoulder and he tilted his head in confusion, “What are you doing? Hold on properly, [Name].”

You glanced away from his gaze and he faintly hears you murmur, “This is kind of… embarrassing.”

_ Embarrassing? _ Osamu didn’t notice it until now that maybe they were being too intimate and whatever blush he had finally managed to get rid of had come back at full blast and he quickly stammered, “J-Just hold on, alright?!”

_ I should just not think about it. I shouldn’t think about this at all. I’m just helping her. Yeah, that’s right. I’m just- _ His thoughts stop and his brain malfunctions when he feels you press up against him even more and your arms wrap around his neck. 

_ I am scum for thinking like this when I’m supposed to be helping her, gods.  _ Osamu shook his head and glanced down once more at you. There was an obvious dust of pink over your cheeks and he closed his eyes tightly.  _ Don’t think about it weirdly. Don’t think about it weirdly.  _

As the two of you break the surface, you find that breathing underwater and on land was more or less the same and you mused, “This is so fascinating.”

“How are you feeling?”

“Really overwhelmed, to be honest,” you softly laughed and then looked up at him, “I can’t believe you though. You just- You just dragged me into the seawater. You know I thought you were mad at me-” 

You were cut off mid-sentence as you sank again since you clearly didn’t know how to float. In addition, even if Osamu was mostly out of the water, you weren’t due to the unfortunate height difference. The water that flowed into your mouth was still strange, and after you spit it out you frowned, “Why didn’t that impede my speaking when I was underwater?”

“I’m not sure, it’s a natural thing that you do subconsciously?” Osamu shrugged and he sheepishly smiled, “I was curious, honestly. I saw your scales and they were really pretty, ya know. But mostly… I wanted to get rid of your fear of the sea.”

“By dragging me in? We’ve only known each other for a few days, I really thought you were punishing me for existing as a fourth-breed.”

“What?!” Osamu’s eyes widened and he unconsciously pulled you closer and lifted you out of water a bit more, “No way! I was-” Osamu paused and he muttered, “Okay, maybe I was out of line, but I didn’t know how else I could’ve convinced you to get into the water.”

He avoided your glare, but after a while you dropped it and laughed, “Thank you, Samu. I’m… I’m really glad I met you. I feel a lot better about myself now, and about who I am.”

You dropped your gaze from his and turned to stare at the horizon. It was breathtakingly beautiful, and even more so when you were directly in the water. Osamu followed your gaze, only to return to staring at your profile. There was such a soft smile on your face, and your eyes were practically brimming tears. You finally tear your gaze away from the horizon to meet his, and a small gasp escapes you when you realize how close he is to you.

Both of his arms were wrapped comfortably around your waist, resting right above where the scales would start, and just below the dorsal fin on your back. There is a small smile on his face, one that you’ve never seen before. You couldn’t name the emotion he had there, but he softly whispered, “I’ll help you from now on.”

“Huh?” 

He took a deep breath and explained, “I originally became curious about you because of your song. It’s a song that our kind uses when we’re looking for a soul mate.”

“A soul mate…”

“Yes, it’s usually only used during our mating seasons, which is why we found it strange that you would know of it, but ya know… it all makes sense now,” Osamu chuckled. It was such a faint and fleeting laughter, you wish it lasted longer. There’s a soft and tender expression on his face and he repeated, “I’ll help you get used to your mermaid side. I don’t want you to live your life afraid of the sea anymore. And besides, you’re curious aren’t you?”

Your eyes widened and he teased, “I can see it whenever I tell you about life down there. There’s this thirst of knowledge and curiosity in your eyes that you can’t hide no matter how hard you try.”

“I’d love to, but what would my mother say?”

“Just tell her the truth,” Osamu shrugged. He slowly brings the two of you closer and closer to the outcrops of rocks where the two of you were at originally. He’s practically floating on his back with you atop of him as he supported your weight completely. “I’m sure her and your grandmother would understand.”

“Understand that I’m going to run off with some merman I met a few days ago so I can learn more about that part of my family?”

“Well, didn’t your grandparents do the same thing?”

_ Oh. _ The realization hit you hard and Osamu finally sees the cloudiness in your gaze fade away as his comment brought light to your eyes.  _ He’s right.  _ You meet his gaze and there’s an unmistakable smirk and on his face and you laughed.

“I guess I really am like my grandmother. I hope mother doesn’t mind.”

“M’sure she won’t once she meets me.”

“You say it like you’re stealing me away,” you teased, it was meant as a jest. After all, you’ve only known each other for a few days, yet you couldn’t deny it. There was an unspeakable attraction and interest that you held for the merman that was holding onto you right now. His gaze softens and the smirk on his face slowly fades into a small smile and he said, “Maybe I am. Or maybe you’ll steal me away, just like your grandmother did with your grandfather.”

Your eyes widened and Osamu just smiled ambiguously before bringing you into the shallow waters. As he sits you atop the rocks, you gently maneuver your tail around for the first time and watch in silence as Osamu circles around the water a few times before he decides to approach you again. As he approaches, you softly ask, “Do you think I can really swim like you do?”

“I don’t see why not,” Osamu shrugged as he pulled himself up onto the ledge. He gently touched your tail, it was the first time anyone touched it, and you weren’t sure what to expect. Perhaps you thought that you would feel the sensation of touch differently, but you don’t. He leaves his hand on your tail and asks again, “Are you sure you’re okay?”

His concern was evident in the tone of his voice and the furrowing of his brows. You gently placed your hand over his and nodded, “I’m fine, just confused. My legs are just… a tail now, I suppose it’s something I’ll have to get used to. But uh, how do I turn back?”

“Well, if we had the potions we usually use, it’d change back instantly once you drank it, but since we don’t… probably about an hour or so. It should feel like you’re shedding off a lot of skin.”

“An hour, huh,” you glanced up at the sky, and while it wasn’t too late in the day, you knew that if you delay the transformation process you might not be home in time before your mother would worry. You frowned and grumbled, “I guess I can’t learn how to swim today.”

“We can always do it tomorrow,” Osamu responded as he patted your tail. “Though you’re going to have to get your tail out of the water for it to start.”

“Oh.”

“I can’t help you there.”

“Yeah, no shit,” you dryly responded as you glanced around for the best place to climb up onto the rocks. Osamu laughed and he said, “I can help give you leverage at least.”

“Are you going to carry me again?”

“Maybe if you take off that dumb dress of yours, you’re a mermaid right now, you got scales to cover your bits.”

“ **Osamu!?** ”

“What?! I’m being honest!” He narrowly misses the punch you aimed at his face and he could see that your face was deep red and he laughed, “I’m serious about the scales, but I’m kidding about taking off your dress. It just slows you down since it’s wet and all.”

“That is… true…” you reluctantly acknowledged him and then your eyes widened, “Oh my god what am I going to do about my dress?”

“Uh.”

“Osamu! This is all your fault, you dumb fish boy!”

“Yer a fish now too, rude!”

“Whatever!” 

You huffed and then turned away from him. There was a teasing and mischievous smile on his smile and you turned to him with a slight pout on your face, “You better take responsibility for all of this. This is just so much to take in at once, I’m overwhelmed.”

“I will, I will, don’t worry,” Osamu lazily responded as he scooted back closer to you. 

“Now come on, help me up, I don’t know how to use my tail.”

“Yes, yes,” Osamu fondly shook his head as he carefully assisted you in getting onto the rocks. It’s strange for him to think that he’d be here too, at the same rocky outcrop where he first heard your voice, where he had first encountered you. And while the developments are nothing like what he expected, he couldn’t help but look forward to what the future had in store for both of you.

Especially now that your siren song had quite efficiently lured him into your trap. 


	2. Floatie

**Summary for the Chapter:**

> It wasn’t your fault you didn’t know how to swim. You weren’t a true mermaid after all!
> 
> Continuation of Prompt #7 for Osamutober

**Notes for the Chapter:**

> Prompt #12 for Osamutober  
> Swim /swɪm/  
> Verb  
> to move in water by movements of the limbs, fins, tail, etc.

“Look, just… move your entire tail fin in one fluid movement. You look like you’re a creaky cog.”

“Okay, rude. Look, I don’t know how to swim as a normal human or as a mermaid, cut me some slack,” you whined as you just let yourself sink lower into the ocean. Osamu sighed as he watched you just sink. For the past few days, you’ve been getting swimming lessons with Osamu. It took a  _ lot _ of convincing from you for your grandmother and mother to give you permission to do so. They were extremely worried, and honestly you don’t blame them. 

In the span of less than a week after you came to visit your grandmother for the summer, you had not only unintentionally caught the attention of a real mermaid with their own mating song, but somehow got convinced to learn how to swim properly as a mermaid. Your family members had absolutely refused in the beginning, they knew how painful it was for you to transform between legs and a fin. 

It wasn’t until you had found out through Osamu who found out through Kita that it’s because of your lack of using your mermaid genes that the transformation was so painful. According to Osamu, Kita has equated it to how mermaids who don’t go on land for a while will experience an overwhelming amount of pain when shifting. He believes it’s the same concept. Osamu though, has no idea, after all, he’s never even bothered going on land.

Although recently he’s been feeling more and more tempted to, especially after every time you bring a lunch box filled with goods that only the surface has. Living underwater limits the types of diets that mermaids can have, and while some mermaids have attempted to bring some surface foods and ingredients down here, they never lasted long enough, and they were never able to reproduce it properly. 

Osamu shook his head out of his thoughts and slowly made his way towards you. He stretched out his arms and got close enough in proximity in order to gently pull you upwards. Your arms naturally wrapped around his neck and he sighed, “How confused are you?”

“Very,” you responded as the two of you surfaced. You shook your head slightly, a futile attempt to get rid of the hair from your face. You eventually ended up pushing it back with your hands and you mumbled, “I don’t really understand how you guys do it? You can literally swim with only your tail fin and that’s it. Meanwhile humans swim with their arms and their legs, yet you guys only use your tail fin to propel yourselves, I just don’t get it.”

“I know you don’t,” Osamu laughed as he helped you sit up on the usual rocks. He stayed in the water and asked, “Does it feel more natural moving it at least?”

“A little? I can move it when I’m sitting here, but I can’t seem to understand how to use it when I’m in water.”

“You did it that one time,” Osamu retorted. He heard you huff a bit and when he glanced back up, you were holding a sandwich to him. His eyes widened in excitement and he asked, “What kind is it today?!”

“Bacon, lettuce, tomato, with some mayonnaise and honey mustard.”

“Sounds good,” Osamu took a bite and hummed lightly, “Is delicious.”

“Glad you like it,” you laughed and you sighed, “I feel like I haven’t made any progress.”

“Well, you’ve gone your whole life without using it, not surprised you don’t know how to swim,” Osamu said in between bites. He loved the foods you brought, and honestly he was glad that he was allowed to even interact with you. He had received such a bad scolding from Kita that he didn’t even have the heart to mess around with Atsumu like they usually did. Although after much discussion, Kita had told him that it was okay for him to keep in contact with you since you were technically a mermaid.

Osamu slowly got up onto the rock to sit beside you. Your shoulders were touching, and so were your arms and he asked, “Does your body feel really sore after?”

“Yeah,” you sighed and then leaned against him. You had gotten so used to physical contact with Osamu after all these days of swim practice that you aren’t even fazed anymore when you feel his touch. It was only when his face got too close that you started feeling weird feelings in your stomach. Osamu gently patted your arm and mumbled, “You want a break?”

“This  _ is _ our break.”

“No, I mean like, a day off or something.”

You turned to face him and he shrugged, unintentionally pushing your head off his shoulders and said, “It’s good to take a break when you’ve worked out too much.”

“I mean, I get it, but…”

“Look, I know you aren’t getting as much progress as you want, but you can always revisit this the day after tomorrow. Spend some time with your family, ya know?”

“What, you trying to get rid of me?”

“No!” Osamu responded far quicker than he had expected to. After all, as much as he wanted you to learn how to swim, he also didn’t want you to hurt yourself while doing so. He enjoyed the time that he spent with you and wanted nothing more than to continue doing so. He averted his gaze and mumbled, “Just don’t want you to get hurt. I promised your family that I’d keep ya safe when we practice, and that includes you getting into all sorts of muscle aches from swimming for too long.”

“Aww, Osamu,” you cooed and wrapped your arms around his torso. He was taken by surprise and lost balance on the rock and slid into the water. The two of you fell in with a splash and as you glanced up at him, a bubble of laughter escapes you, “Isn’t this just like the first time you carried me back to the surface?”

“Yeah, but this time you pushed both of us into the water,” Osamu chuckled as he gently held you in his arms. He shifted slightly so you were more at eye level and upon realizing that the two of you were easily drifting around, his eyes widened and he gasped, “Wait! This will work!”

“Hmm?”

“You know how humans use those weird floaty boards you showed me on that slab of yours?”

“It’s a phone, Osamu.”

“Yeah, whatever, that thing,” Osamu rolled his eyes and continued, “What if you just follow the movement of my tail fin with yours?”

“So… I’ll use you as a kick board essentially.”

“Yes, but you’re not kicking, you’re just… moving your tail,” Osamu’s words drifted off and he asked, “Is this a bad idea?”

“No? Or at least, I don’t think so.”

“So, you wanna try it out?”

“Sure! Although,” you glanced up at the surface. The slight change in the lighting indicated it was getting dark and you laughed, “Maybe tomorrow?”

“Oh, it’s late, huh?” Osamu mumbled. He hadn’t noticed that the sun was already beginning to set when the two of you had surfaced earlier for a snack break. He frowned for a bit, but your finger that gently poked between his eyebrows where there was a crease made him snap out of his thoughts.

“It’s okay! We can continue this tomorrow!”

“Mm, if you say so, hopefully we can make more progress.”

“Hopefully!” you laughed and smiled, “Let’s get back up, shall we?”

“Yes, yes,” Osamu fondly shook his head as you patted his shoulder as though he was a horse. He picked up his speed and when the two of you broke the surface, honestly, he was glad that you were struggling to learn to swim. While it may be frustrating for you, he was happy to have an excuse to hang out with you and hold you so close to him. 

Was it selfish of him to have such thoughts? Maybe, but that’s fine - as long as you don’t find out yet.


	3. Important

**Notes for the Chapter:**

> Prompt #25 for Osamutober  
> memory /ˈmɛm ə ri/  
> noun  
> the mental capacity or faculty of retaining and reviving facts, events, impressions, etc., or of recalling or recognizing previous experiences.

Osamu will always remember the first time you had opened up your thoughts about your mermaid side. It was two days after you had finally learned to swim, and a day after you had shown your family your mermaid form. Osamu was there when it happened. 

He had stayed a little bit further away in the deeper parts of the ocean watching over you. He knew that you could swim now, and while you weren’t capable of going at extremely fast speeds, or breaching the surface like he was able to, he was still worried that perhaps you may get a cramp in your tail. You’ve been getting them every now and then, and it was always an absolutely horrifying moment every time it happened. 

It was as though an entire electric shock would go through you and it would render you completely unable to move. The first time it had happened, he had never realized how terrifying it was to just sink and being completely unable to move your tail. He had heard your sudden cry of pain and the weak calling of his name and never in his life had he swam so quickly to you. 

His arms that had wrapped around you became your safe haven, and he was the pillar that kept you grounded and supported you through everything. Honestly, if it weren’t for him, you wouldn’t have had the courage to even show your family your mermaid form. While they were supportive of you, you couldn’t help but harbor doubts that they probably didn’t want you to ever even consider that part of you. Perhaps it was a part of you that they wanted to remain ignorant to.

Oh, how wrong you were. 

When you had hesitantly and nervously brought up the topic during dinner, you still remember your grandmother dropping her fork on her plate. You couldn’t meet her gaze, yet instead of anger or anguish, there was so much hope and joy in her voice that you had nearly broken into tears yourself. Upon meeting her gaze, your grandmother was slowly wiping away the tears that had gathered at the edge of her eyes, all while happily nodding her head about how glad she’d be to bear witness to it.

The day that it happened, your grandmother and mother had found a safer and easier to access location near the rocks as you mentally prepared yourself to dive in. As confident as you were that you could successfully swim, the real question was how your family would react to seeing you as a mermaid. You had nervously glanced around for Osamu, and you had barely seen a glimmer of his tail before it disappeared below the waves. 

A glimmer was all you needed, for it was the one thing that seemed to keep you going. You took in a deep breath and dove straight into the water, and unlike the first time, or the third time, you transformed, it was a fluid transition from human to mermaid. Your family watched in awe, and so did Osamu, as you touched the water and your body shimmered in the sunlight as your scales reflected the light. 

You were practically glowing, and honestly, Osamu felt a swell of pride as he watched you swiftly and easily twist, turn, and spin in the water. You weren’t completely one with the sea yet, but you were definitely getting there as you continued to practice. Your grandmother had nearly broken into tears, and your mother was stunned into silence. Between the three of you, only you and your grandmother have ever come in contact with a mermaid in their true form. 

You slowly swam up to them and your mother knelt down and extended her hand to you. You reached out and she softly mumbled, “You look beautiful, [Name].”

“Your scales are the same as your grandfather’s,” your grandmother softly spoke up in between sobs. She had calmed down a little, and honestly she was just so stunned. You beach yourself onto a rock and extend your hand for your grandmother to hold. She carefully takes your hand into both of hers and she smiled, “It makes me so happy to see you so happy like this. Truly, I am.”

“You and mom don’t think I’m disgusting?”

“Oh darling, never!” your mother shook her head firmly and then chuckled, “You are our precious pearl, one that shines like none other. To see you this happy, it takes me over the moon, you know.”

“So tell me, sweetheart, the boy who taught you to use your fins.”

“Osamu, his name is Osamu,” you softly mumbled and then looked out over the sea. You were certain he could hear you, even if he didn’t want to be anywhere near you and your family, you knew he was listening. “I owe him so much, if it weren’t for him… I wouldn’t have had the courage to actually go back into the sea, nor would I have had the courage to show this side of me to you two.”

Your grip on their hands tightened and you softly mumbled, “Thank you for accepting both sides of me, mother… and grandmother.”

“Oh, darling,” your grandmother gently squeezed your hand tighter and she chuckled, “We love you no matter what you look like. You will be our beautiful precious child no matter what.”

The rest of that day was filled with so much familial love that Osamu didn’t have the chance to say anything to you. The only sign he gave you before he left was a quick slap of his tail breaching the surface before he disappeared beneath the waves. Your grandmother and mother didn’t catch the brief moment of his silvery tail breaking the orange and pink sunset waters, but you barely did. Perhaps it was due to having better vision when you were in your mermaid form, but you eagerly slapped your tail against the surface of the water.

And no matter how far away he was, he still heard the distinct sound of your tail fin hitting the water and he smiled. Even if he couldn’t see you today in person, he was glad that he got to bear witness to such an important moment for you.

***

The day after, he remembers how you had shown up a little later than usual. Honestly, he wasn’t sure if the two of you were going to continue meeting up like this. It’s been several months since he met you, and the two of you have gotten close enough to the point where skinship was only natural between each other. He didn’t want to admit that he was in love with you, it was such a strong word, and even more so when used with another mermaid.

After all, to love one another would mean that they were only committed to the person they chose. There was no other option after that, and as much as Osamu adored you and wanted nothing more than to spend every waking moment with you, how could he do so when you were not a full mermaid. Your hybrid nature makes it hard for him to confess, even if it’s always at the tip of his tongue every time he parts way with you after every swimming session.

He sighed as he let the water ebb him to and fro beneath the surface. His eyes were closed, yet his face still wanted to feel the faint sunlight that filtered through the surface over him. The feeble light was nothing in comparison to how it felt above the water, but it was still a comforting feeling especially since he had started to associate it with your presence.

“Osamu!” Your voice was muffled as you approached and he remained below the surface, still contemplating thoughts of you. “Osamu?” 

You squinted as you tried to see past the reflecting sunlight, and upon seeing the ever familiar silver scales beneath, you shook your head and slapped the surface a few times with your hands to get his attention. 

Osamu’s eyes slowly opened, and he could see your visage slightly distorted due to the waves and he swam upwards. As soon as his head appeared above water, you laughed, “Were you lost in thought again?”

“Kind of,” Osamu weakly admits and then slowly pulls himself up onto the rock. You take a seat beside him and naturally help him push stray strands of hair out of his face. There’s a faint smile on your lips and you asked, “What were you thinking of?”

You asked it so naturally that he hesitated for a moment before softly admitting, “Thinking about you.”

“Me? I’m flattered,” you giggled as you finally finished fixing his hair for him. He smiled in return and you asked, “Are you wondering about what we’re going to do now that I can swim?”

His eyes widened in surprise, it was almost as though you knew exactly what it was that he was thinking of and you smiled, “I don’t want to stop meeting up with you, Osamu.”

Your gaze turns to the ocean and you extend your legs so they dip into the water, and already you can see the faint shimmer of your scales showing up, and you weakly smiled, “I’m still only a novice. I don’t know a lot about what it’s like to be a mermaid, I want to know more, and I guess… most importantly, I just want to spend more time with you, is that weird?”

Osamu knew you were rather unflappable at times. Even the skinship the two of you shared didn’t really embarrass or fluster you as much as it normally would have. If anything, it always felt like he was the one that was hyperattentive to you. Yet at this very moment, it felt as though finally he could see what was hidden within you. 

The faint blush of pink as you made eye contact with him deepened into a darker shade of red and he softly mumbled, “No.”

His hand gently reaches out for yours and he laughed, “I didn’t want you to suddenly disappear on me either. I enjoy hanging out with you, and even more so whenever you bring me snacks.”

“So you just want me around for snacks, you snack thief!” you laughed as you lightly bumped him with your shoulder and said, “You know when you said you’d help me learn to swim, I was hoping it wouldn’t just be that.”

“What else would you want me to teach you?” he asked as his fingers naturally intertwined with yours. You gave him a reassuring squeeze as you leaned against him and you said, “I don’t know. Hunting? Lifestyle? I kind of want to meet your friends, but…” you worriedly glanced down to your tail and asked, “Would they accept me?”

“I don’t see why not,” Osamu shrugged and then added, “I’ll fight them if they’re mean to you.”

“Haha, if you say so,” you said. You glanced behind you and said, “Oh yeah, I brought your favorite today.”

“Onigiri?!”

“Yup! I made the one with Chicken Karaage since you said you liked that one the most last time.”

“Yes,” Osamu licked his lips from the mere thought of food, and as you brought out the small bento box and placed it on your lap, Osamu struggled between letting go of your hand, or grabbing the onigiri. Yet your next course of action takes him by surprise as you lift an onigiri to his face and offer him the first bite. He gratefully takes it, glad that he doesn’t have to choose between eating or letting go of your hand. 

After he eats a bite, you take a bite from the same onigiri and you hummed, “I think I did pretty good today.”

“It’s good,” he reassured you and then nudged you for another bite and you laughed, “Alright you big puppy.”

“Woof?” Osamu asked as he splashed his tail against the water’s surface. The mist of salt water that came up made you close your eyes as you attempted to bring the onigiri to Osamu’s face, only for you to accidentally just smush the entirety of it against his cheek.

He blinked a few times and whined, “[Name]!”

“Don’t whine at me! You splashed me with saltwater, you dummy!” you shook your head as you tried to salvage the onigiri. Osamu pouted while he chewed on the onigiri, but at the same time, this was okay. You were carefully picking the rice off his face, all while complaining about how it was such a waste of food, and that salt water doesn’t mix well with onigiri. 

“Sorry.”

“You better be, don’t ruin the onigiris I worked so hard on making for you!”

“What’s the occasion?”

“A thank you for teaching me to swim.”

“Ah,” Osamu nodded and then he glanced up at you and said, “You got somethin’ on your cheek.”

“Hm?”

“Right here,” Osamu leaned forward and licked the rice grain off your cheek, and then proceeded to lick his lips after. You blinked a few times and you stuttered, “W-What the heck?!”

“What? I was helping you get rid of the stray strand of rice.”

“You, you can’t just lick it off of me,” you explained with an exasperated sigh. “Are you telling me that you lick food off your mermaid friends’ faces?”

“No, just you,” Osamu responded and then tilted his head, “You’re different from them.”

“I am?”

“Yeah, you’re-” Osamu paused and then softly mumbled, “You’re different from them, but you’re more important.”

“I’m important to you?”

“Of course you are, why wouldn’t you be?” he frowned and then continued, “I like you a lot, you know.”

There was a silence, and it wasn’t until after Osamu had said what he said that he realized what he just did. He sat there, mouth full of onigiri, and frozen. He wasn’t entirely sure if he had crossed the boundaries of friends between the two of you, and honestly he wasn’t sure if he had done something wrong at this point. 

As good as the onigiri tasted, he found himself struggling to swallow after that unintentional confession. After he forces himself to swallow, he slowly turns to look at you, and is surprised to be faced with a soft and bright smile. 

“You know Osamu, I like you a lot too.”

His eyes widened and you softly continued, “You’re important to me too. Now come on, let’s finish the onigiris.”

_ Wait. _ Osamu frowned as you grabbed another onigiri.  _ Does she not- does she not realize that I just confessed to her? _ He watched you in disbelief, as the realization sunk in, he couldn’t help but laugh out loud at how dense you were.

“Hm? What are you laughing about?”

“It- It’s nothing,” Osamu managed to choke out between his laughter. You tilted your head in confusion and asked, “Is it something I did?”

“No, no, it’s nothing, [Name].”

“Are you sure?”

“Yeah, I’m sure, don’t worry about it,” he chuckled as he gently squeezed your hand to reassure you. You tilted your head at him slightly before shrugging and saying, “Alright, you weirdo. Now come on, let’s finish eating and then we can do some more swim practice!”

Osamu nodded, and honestly this was fine. Even if you were dense, at least it meant that he could continue to spend more time with you, and perhaps maybe in the future, he’ll be able to properly confess to you later on.


	4. Responsibility

**Summary for the Chapter:**

> He was in love with you, irrevocably so.

**Notes for the Chapter:**

> Prompt #26 for Osamutober  
> addicted /əˈdɪk tɪd/  
> Verb  
> compulsively committed or helplessly drawn to a practice or habit or to something psychologically or physically habit-forming (often used in combination)

“You… You want to bring her down here, and introduce her to our people?” Atsumu grumbled and Osamu sighed, “Look, I know you guys are against it, but she… she is one of us.”

“Well, I’m not against it,” Suna shrugged and said, “If Kita says no, that’s that though. You know how strict the rules are.”

“I don’t get it, you guys let Atsumu go up to the surface all the time to meet his soulmate, yet I’m restricted?”

“I don’t think ya get it, Samu. I courted Hinata fair and square. You’re the one that’s being courted by your girlie up there.” Atsumu frowned and continued, “She sang the song and you’re the one that responded, it’s not supposed to be like that.”

“Even if we yell at him and nag at him, I do believe it’s too late for Osamu to suddenly change. He’s emotionally attached to her, and you know how our species are when we get emotionally attached,” Suna sighed and then added, “You can’t just complain at Osamu to suddenly and abruptly stop seeing her, it’ll ruin his entire emotional and mental state.”

Atsumu bit his lower lip and grumbled, “Why did you have to fall in love with a human, god damn it?”

“You did too, and I don’t see why everyone’s okay with you and your soulmate!”

“At least my soulmate realizes what we are unlike yours!”

Atsumu’s retort stung, and for the first time, Atsumu regretted that retort. He did not miss the way his twin’s face had flickered with pain and anguish and before he could apologize, Osamu mumbled some excuse before escaping the situation. Suna sighed and glared at Atsumu.

“I.. I didn’t mean-”

“You  _ know _ how much that shit hurts. Osamu’s probably suffering the most from this.”

“What is Osamu suffering from?” 

Atsumu and Suna momentarily froze before they stiffly turned around to see Kita and Aran approaching. Kita tilted his head to one side and asked, “Well?”

“It’s… It’s [Name], the hybrid girl that Osamu was unintentionally chosen by,” Suna started and then went on to explain what was happening. Kita let out a sigh and shook his head, “I do not believe we have any right to interfere.”

“He’s going to get hurt!” Atsumu shouted. There was silence and Atsumu softly continued, “I don’t want him to get hurt… From the way he talks about her… I can’t help but feel like he hasn’t actually confirmed that the two of them are together, so as a result he’s kind of just… simmering in doubt.”

“He will be fine,” Kita reassured Atsumu with a pat on his shoulder and the smile on Kita’s face was eerily all-knowing and he continued, “It’s a rough period, but I am sure both of them are going through a struggle right now.”

***

“[Name], sweetie, you didn’t eat much tonight,” your grandmother gently commented. You glanced up from the plate of food and sheepishly smiled, “I have a lot on my mind.”

“Do you want to talk about it?”

You slowly put down your fork and mumbled, “It’s Osamu.”

“Your mermaid friend who taught you to swim, correct?”

“Mhm,” you nodded and then softly asked, “Is it weird that I want to spend so much time with him? Being with Osamu just… makes me really happy. Sometimes I wonder if I’m allowed to be this happy with him, especially since well… he’s a full on mermaid and I’m not.”

You heaved a sigh and your shoulders dropped with it, “Sometimes I feel like I’m interfering with his life since he spends nearly every day with me… But I.. I really enjoy each and every moment I spend with him. I don’t want him to lose a part of himself because of me.”

“You care for that boy a lot, don’t you?”

You nod and hesitantly responded, “I… I feel like I’m always thinking about him. Every moment of the day seems to be consumed with thoughts of him and I’m just… I don’t know what to do.”

“Have you tried speaking to him about it?”

“N-No, how am I supposed to admit something like this to him? It’s embarrassing!”

“But you trust him, don’t you?” your grandmother chuckled as she gently patted your head. Her fingers carefully threaded through your hair and she smiled, “I am sure he’d be happy to hear your thoughts, [Name].”

“But how can you be so sure, Grandmother?”

“Trust me, sweetheart,” she chuckled after one last pat on your head. “Trust me.”

***

“Osamu!” you ran up to the rocks where Osamu was already sitting and he barely manages to greet you until he sees what you’re wearing. A simple swimsuit, and while yes, he has seen you in your mermaid form, you’ve always worn a tank top of some sort on top. So seeing you in a swimsuit was a treat that he wasn’t completely ready for. His eyes widened at how much skin was exposed, and even though you were wearing one of the cute two-piece swimsuits with a skirt, there was just still so much exposed and he wasn’t quite sure where he could look beside your face without feeling indecent.

The blush on his face was unstoppable and as soon as you realized it, you glanced down and almost immediately moved your arms to cover your chest and you softly mumbled, “W-What? Do I look weird or something?”

“N-No, you look… great,” Osamu softly responded.  _ Beautiful. _ That was the first word that came to mind, and honestly as much as he wanted to tell you that, he had to look away. It was as though he was looking at the sun itself, you were so brilliant that he couldn’t stare right at you. He hears you clear your throat and when he turns back around, you have a towel draped over your shoulders, and over your chest. Your face was still dusted with a pretty pink and you mumbled, “Sorry, maybe I shouldn’t have worn this.”

“No! I-” Osamu stopped his words and dragged a hand down his face, “You’re killing me, do you know that?”

“E-Eh?! What do you mean?!”

“Never mind, just… you’re beautiful,” Osamu softly whispered. He had desperately hoped that the waves would carry his voice away, yet he could see how your eyes widened and there was a smile that tugged at the corners of your lips and he asked, “What made you change your outfit?”

“My grandmother bought it for me. She told me I’d look cute in it… so I wanted to show you,” you explained as you took a seat next to him. He felt even more aware of the physical contact between you and him, but he maintains eye contact with you anyways. He does a quick glance over your outfit, and he can’t stop the small, soft smile from tugging at the corners of his lips.

“You’re beautiful.”

“You-” your breath hitched for a split second and you mumbled, “You’re going to make my face all red, Osamu!”

“Your face already is red,” he pointed out and you bumped his shoulder, “Shut up!”

There were peels of laughter between the two of you and you softly said, “It’s also because I wanted something easier to change in and out of when I switch.”

Osamu nodded, and then his mind went blank. The sudden realization of what that entailed caused his brain to combust and he stared at you blankly before softly asking, “You’re… you’re willing to show-”

“Don’t say it out loud! Stop! But… yes, I’m willing, I.. I was insecure about how my mermaid form looked but.. You always tell me that I’ll be fine, I want to trust your words.”

Osamu cleared his throat and quickly stammered, “You should go in first, I’ll wait up here.”

You stared at him and he added, “I won’t look! I promise! Here, you can blindfold me with your towel.”

“Alright, fine, I trust you, just- just stay up here, okay?”

You drape the towel over his face and he lets out a breath that he didn’t realize he was holding in. He had no idea why today of all days felt even more nerve wracking to him, perhaps it was due to the conversations that he held with Atsumu - although they were more like arguments. He heard the distinct splash of water, and soon the towel that was draped over him was taken off. 

You nervously hold the towel to your chest, and while you know that there are scales that cover you properly, the notion of it was still strange to you. You had wrapped your swimsuit in the towel you had previously draped over Osamu and even after you pulled it off his head, his eyes were still tightly shut. The smile on your lips widened at how loyal he was to you and you softly said, “You… you can look.”

Osamu slowly opened his eyes and upon seeing you in all your glory, he couldn’t help but let out a small gasp. He always knew the crystal opal sheen on your scales would look even prettier when fully exposed to the sunlight. The iridescent and rainbow hues that reflected off your scales were dazzling and he softly smiled, “I’ll say it again, but you’re beautiful.”

“Stop flattering me,” you muttered and glanced away. Osamu’s smile widened and he cheekily responded, “But I’m not.”

He loved how the flush on your face deepened and he offered you his hand, “Wanna go for a swim?”

“Well yeah,” you responded with a slight scoff. You playfully rolled your eyes as you took his hand. As soon as his fingertips touched yours, his grip tightened and he pulls you into the water with him. Your towel left abandoned on the rocks, and safely tucked away hidden from view of others. As soon as you fall into the cold ocean water, you shiver from the change in temperature and Osamu laughed, “Cold?”

“Kind of, it’s weird feeling the water and everything so… directly.”

“Does it feel weird?”

“No. I just feel more hydrodynamic.”

“See, told you your clothes slowed you down,” Osamu shook his head fondly and he asked, “Should I let go?”

He glances at your hand that’s intertwined with his and you shook your head, “Nah, I like swimming like this. So when I get lazy I can just hold onto you.”

“Wow, okay,” Osamu pouted before breaking into a small laughter. “Come on, I wanted to show you a place I found recently while patrolling.”

“Hmm, what kind of place is it?”

“You’ll see.”

“Alright, fine,” you laughed as you swam by his side. It was like the equivalent of going on a walk while holding hands with someone. The two of you fluidly moved through the water, although honestly, Osamu was having a hard time looking at his surroundings knowing that you were right there, right next to him, in all of your glory. 

While he blatantly admired your appearance, he was still listening to your ramblings about how amazing it was below the surface, even more so when you were capable of seeing so much now that your vision has finally adjusted. The darkness was no longer a real issue, and as Osamu told you, the more you practice using your mermaid parts, the more likely you’ll adapt easier.

The smile on his face was borderline fatherly. After all, seeing you go from being fearful of water to being able to swim so freely and unrestrained made him proud of your development. He unintentionally squeezes your hand, and you glance at him, confusion clearly written all over your face before you squeeze his back and give him a cheeky grin. A small, quiet laugh escapes his lips as he continues to pull you deeper below the surface. The sunlight could barely reach the depth you were entering and Osamu’s eyes narrowed slightly, and it was during that split second of him narrowing his eyes that you remembered that mermaids were indeed considered an apex predator. 

His pupils would dilate and his iris would glow a faint gold. It was but a fleeting moment, but you could feel the water almost still as all wildlife that inhabited the area seemingly disappeared as soon as he did that. You gently squeeze his hand, and when he glances over to you, he looks perfectly normal again and you ask, “What did you just do?”

“Oh, you mean with my eyes?” Osamu asked as he pointed to them with his free finger. There was a teethy grin, and you weren’t sure if it was because he had activated whatever it was that he had activated, but his teeth seemed extra sharp, almost like shark teeth. You tilted your head to the side and Osamu continued, “I asserted my dominance.”

“You asserted your dominance?”

“Yup, making sure nothing else would be around, and if they dared… well, they wouldn’t,” Osamu chuckled lowly. But although he was laughing externally, the gaze in his eyes were serious. You trusted him, but instinctively inched a little bit closer to him and he laughed, “You’ll be safe with me, [Name].”

“I know, I trust you, but you always warn me about how dangerous it can be down here and besides, if you guys exist, then Krakens and Leviathans probably exist too, right?”

“They do,” Osamu nodded and then added, “But we’re far too close to the surface for their liking.”

“This is too close?”

“You have to be like below 1500 kilometers to run into them, you know?”

“Oh, can we even go that deep?”

“Some of us can,” Osamu proudly smiled and said, “I know I can, but most of us aren’t used to it. I normally patrol the deeper regions since I have better vision than most. Anyways, we’re here.”

Osamu led the two of you into a small cavern, but as you went deeper in, it almost seemed as though it was growing brighter instead of darker. You frowned in confusion, but as Osamu pushed aside the stray strands of kelp that blocked the entrance, your eyes widened in shock. 

“What is this?”

The room was filled with glowing coral, each of them pulsating their own colors and gradient. But even more enchanting was the giant shell that laid at the center of the cavern. The shell had a slight opening at the bottom and it was clear that nothing inhabited the inside, yet there were coral and all sorts of vegetation that were strangely glowing or illuminated in some sense that just reminded you of a starry sky below the waves.

“A cavern filled with bioluminescent sea life. I came across this place when I was trying to chase down a jellyfish.”

“You were chasing a jellyfish?”

“They taste good, okay?”

“Alright,” you took his word for it, and you slowly swam up to the coral and you whispered, “Can I touch it?”

“Mm, not sure, I wouldn’t though. Don’t know if it’ll electrocute you or if it’s poisonous.”

“Oh,” you frowned and retracted your hand. Osamu glanced over you and he said, “This cavern reminded me of you.”

You looked at him in surprise and he continued, “It’s breathtakingly beautiful, and each of them shine and glow in their own way, just like you.”

He doesn’t dare to look at you, but he’s hoping that he was able to convey his feelings properly. On the other hand, you could only stare at his side profile the entire time in shock, and again you felt that same pounding of your heart and the butterflies in your stomach. Your grip on his hand tightened, and when he turned to look at you, you quickly hid your face by hugging him tightly. It took him by surprise and he softly asked, “Is something wrong?”

“No.” Your answer was muffled, but you really didn’t want him to see your face right now. You were certain that you looked like a fool. You could feel your face heating up and every compliment he gave you only made it worse. His arms slowly wrapped around your waist, holding you close against him and he remained silent. 

For once, he was glad that you had initiated the hug first, cause as much as he wanted to hold you, he knew it would be weird if he did it without your permission. Right now, he simply wanted to hold you a little bit closer, just a bit tighter, and so he did. He turned his gaze away from the beauty of the cavern to gaze upon you instead.

He loved you. He knew this for a fact. He knew it in the way he’d gravitate to you. He knew it from how he hung onto every single word you said, and how he cherished every smile that he brought onto your face with the laughter of yours that just seemed to melt away every single insecurity he had. 

_ I love you, even if everyone else is against it, I really do. _ His grip around you tightened, and you glanced up to see Osamu staring down at you. Your eyes widened at the sight of his face. There was a painful smile, and it almost seemed like he wanted to cry. You let go of him, and in return he lets go of you, but instead of you making space between the two of them you swam upwards so you were eye level with him, and you softly asked, “What’s wrong?”

His eyes widened from your question and you softly murmured, “You look like you’re about to cry, Samu.”

His hands slowly reached up to his face and he mumbled, “I… I don’t know, I was just…”  _ thinking about how much you mean to me.  _ He bit back his words, and you could tell he did from how he averted his gaze for a split second before returning with a strained smile. It was almost more like a grimace rather than a smile and you softly asked, “Do you want to talk about it?”

He hesitated and then said, “I… I was thinking about you, and how much you mean to me.”

Your eyes widened and he quickly added, “Let me.. Let me explain.” 

His voice was laced with desperation, a tone you’ve never heard him use before. You nodded, but your hands on his cheek never left and almost naturally Osamu’s hands came back to rest around your waist. 

“Do you remember how I told you the song you sang was one for mating and to find your soulmate and all?” You nodded and he continued, “Usually… usually the person who can hear your song is the one you’re tied down to for life. Mermaids, we.. we don’t ever find another partner once we choose our first. And well,” he hesitated, and he isn’t looking at you anymore. He doesn’t want to see the potential rejection on your features. 

While he knows that there’s the possibility that you won’t reject him, he can’t bear it. He can’t stand knowing that there is the chance that his feelings won’t be reciprocated, and honestly, after he’s committed so much time and emotions on you, he doesn’t know if he can just move on and find a new soulmate. It wasn’t something that mermaids did. 

You can see the anguish on his face and it was then that you realized that maybe, just maybe, he was experiencing the same thing you were. Heart racing, stomach fluttering, and your thoughts were just constantly filled with him. Was this what your grandmother was alluding to all this time? 

You gently applied pressure to his cheeks and you whispered, “Look at me, Osamu.”

He reluctantly looks at you, but when he sees such a soft smile on your face, he finds it hard for him to breathe. You really did manage to steal his breath away at every opportunity possible. 

“I won’t leave your side.”

His eyes widened at the implication of your words and you continued, “I want to be with you. I want to spend every moment with you. I… I really like you, do you know that?”

_ “I really like you, do you know that?” _

Those were the words he’s been waiting for, and not the dumb platonic kind that you had stated last time, but the romantic ones. The ones that practically sealed the deal that you felt the same way. You watched with amusement as his eyes widened and his lips curved into a bright smile. He pulled you closer to him and he asked, “Are you being serious right now? Is this a dream?”

“It’s real,” you laughed as you felt him gently spinning the two of you in the water and you asked, “Do you think I’d be dumb enough to confess without feeling like I was certain of it?”

“You- I confessed to you that day you told your family about being able to swim and you brushed me off!”

You blinked a few times and sheepishly asked, “Did I?”

“Yes!” Osamu sighed, but then laughed as he pressed his forehead against yours. “Gods, I was… I was so worried this was going to be one-sided forever.”

“Why would you think that?”

“It felt like you weren’t interested in me, just swimming and learning more about me.”

“Samu, if I didn’t like you, I wouldn’t let you always hold my hand or keep me close. Besides, I’m slow,” you weakly admitted and looked away. “I had no idea I was infatuated with you until I told grandmother about it.”

“Oho?”

“Oh shut up, don’t give me that look,” you futilely pushed him away, but he laughed as he held you closer. Your strength was much less than his, and he could easily hold you close if he wanted to. He gently nuzzled his nose against yours and mumbled, “So, does this mean-”

“Yes, Osamu, we’re dating, lovers, partners in crime, significant others,” you teased. You gazed right into his eyes and you smiled, “So take care responsibility for me, okay?”

“I will, I promise you.”

**Notes for the Chapter:**

> I swear this is the last chapter.

**Author's Note:**

> I have no idea what I was writing. This is what happens when you try to fit something into a one shot and by the end of it you aren't even sure if it turned out well. Might come back and revisit this to make it a chaptered fic, but I mean, we'll see what happens to me by the end of this month with how Osamutober is just a collection of plot bunnies coming to life and drowning me in fluff.


End file.
